In Young’s double-slit experiment, the slits are separated by $0.28~\text{mm}$ and the screen is placed $1.4 ~\text m$ away. The distance between the central bright fringe and the fourth bright fringe is measured to be $1.2~\text{cm}.$ The wavelength of light used in the experiment is:
1. $600~\text{nm}$
2. $500~\text{nm}$
3. $400~\text{nm}$
4. $200~\text{nm}$

In Young’s double-slit experiment using monochromatic light of wavelength $\lambda,$ the intensity of light at a point on the screen where path difference $\lambda$ is $K$ units. What is the intensity of the light at a point where path difference is $\lambda/3$?
1. $\dfrac K3$
2. $\dfrac K4$
3. $\dfrac K2$
4. $K$

In a double-slit experiment the angular width of a fringe is found to be $0.2^\circ$ on a screen placed $1 ~\text{m}$ away. The wavelength of light used is $600 ~\text{nm}.$ What will be the angular width of the fringe if the entire experimental apparatus is immersed in water?
(Take the refractive index of water to be $4/3$).
1. $0.33^\circ$
2. $0.20^\circ$
3. $0.15^\circ$
4. $0.10^\circ$

What is the Brewster angle for air to glass transition? (Refractive index of glass = 1.5.)

1. $49.{29}^0$
2. $43.{21}^0$
3. $50.{30}^0$
4. $56.{31}^0$

What is the distance for which ray optics is a good approximation for an aperture of 4 mm and wavelength 400 nm?

1. 40 m
2. 30 m
3. 20 m
4. 50 m

When the light diverges from a point source, the shape of the wavefront is:
1. Parabolic
2. Plane
3. Spherical
4. Elliptical

When the light is coming from a distant star that is intercepted by the earth, the shape of the wavefront is:

The refractive index of glass is $1.5$. What is the speed of light in glass? 
1. $2 \times 10^{8}~\text{m/s}$
2. $3 \times 10^{8} ~\text{m/s}$
3. $1.5 \times 10^{8} ~\text{m/s}$
4. $2.2 \times 10^{8}~\text{m/s}$

Which of the following is not true?

A beam of light consisting of two wavelengths $650~\text{nm},$ and $520~\text{nm},$ is used to obtain interference fringes in Young’s double-slit experiment. What is the distance of the third bright fringe on the screen from the central maximum for wavelength $650~\text{nm}?$